Travel Demand Model - OKI

OKI/MVRPC Travel Demand Model – Version 6.04. Home-Based Work Model Estimation4.1 Sample SizeThe final dataset used for estimating the HBW mode choice model consisted of 7514observations, of which a total of 7021 were available for estimation. The excluded records includeintrazonal trips, records where the chosen mode was transit but no transit path was available 1and records with a highway in-vehicle time longer than 60 minutes. The latter amount to lessthan 1% of the total, and are considered outliers. Table 4.1 shows the number of records bychosen mode. A common rule of thumb suggests that at least 300 records per mode arerequired to obtain robust estimation results. In this particular case, the relatively few recordswith chosen mode park & ride and kiss & ride suggest that these submodes will most likely needto be collapsed. Table 4.1 also shows the modal shares, i.e., the weighted number ofobservations. Please see Section 3.3 for an explanation of the weight factors. All estimationresults were derived using estimation weight factors, as corresponds given that the sample ischoice-based.Table 4-1 Home-Based Work Sample SizeMode ChosenNo. ObsModalSharesDrive Alone 4480 84.70%Shared Ride 2 482 9.11%Shared Ride 3+ 157 2.97%Local BusWalk 907 1.53%Park & Ride 54 0.09%Kiss & Ride 15 0.02%Express BusWalk 782 1.32%Park & Ride 125 0.21%Kiss & Ride 19 0.04%Total 7021 100.00%Modal shares are weighted proportions.The HBW estimation dataset includes all HBU records. This is necessary because there are fewHBU observations, and certainly not enough to estimate even a simple model. People makinghome-based university trips are considered to behave more like people making HBW trips thanpeople making other types of trips, and for this reason the HBU model is estimated jointly withthe HBW model. The HBU mode choice models however will be calibrated separately from theHBW models.Table 4.1 assumes that all trips using a "mixed service" route during the peak period areconsidered express bus trips, while similar trips during the off peak period are considered localbus trips. In the initial estimation runs it was assumed instead that all "mixed service trips" werelocal bus trips. In the end, however, it was preferred to collapse the local and express trips as asingle transit mode, for several reasons: uncertainty regarding the identification of express bustrips, no fare differential for express service relative to local service, and unsatisfactory1 The model may fail to find a path for several reasons: survey reporting errors, survey geocoding errors orerrors in coding the transit lines or the transit connectors. In addition, Tranplan limits the maximumweighted travel time to 255 minutes, so very long transit trips do not get a path assignment.Mode Choice - Home-Based Work Model Estimation 17